1. Field of the Invention
The present invention relates to a heat transfer film having excellent transferring properties and excellent adhesion of ink which gives clear images in a heat transfer printer. In particular, the present invention relates to a thermoplastic resin film which is a melt heat transfer film having excellent transferring property and excellent adhesion of ink in various printing systems.
2. Discussion of the Background
A variety of systems have been used for recording images and information, for example, a sublimation heat transfer system, a melt heat transfer system, an electrophotographic system and an electrostatic recording system. In these systems, a heat energy is used for the transfer, fixing and adhering of images. For example, a system is known wherein an ink ribbon is pressed onto a recording medium and a coloring material is transferred from the ink ribbon to the recording material. In another system, a toner is transferred to a recording medium and adhered to the recording medium by heating a high-temperature roll or light.
A melt heat transfer system which is generally used for information recording for example, for bar codes is explained in the following. As shown in FIG. 1, a heat-transfer ink ribbon 1 composed of a heat-melting ink la and a base material 1b for supporting the ink and an image-receiving film 2 are inserted between a printing head 3 equipped with a thermal head as a heat source and a drum 4. The thermal head is controlled using an electric signal and the heat melting ink 1a in the heat-transfer ink ribbon is heated. The molten ink is directly transferred to the image-receiving film 2. Ic denotes the transferred ink.
The support itself may be used as the image-receiving film in a melt heat transfer system. A layer of a polyester resin or an epoxy resin or a primer layer having good adhesion to a heat-melting ink is frequently formed on the surface of the support.
Examples for the support of the image-receiving film are a pulp paper, a synthetic paper made of a stretched film of a propylene resin containing an inorganic fine powder such as a burned clay or calcium carbonate a stretched film of polyethylene terephthalate; a polyolefin resin film; a coated synthetic paper, wherein the whiteness and the dyeing property are increased by coating a pigment coating agent containing an inorganic fine powder such as silica or calcium carbonate and a binder on the surface of the above-described film or paper.
A synthetic paper obtained by stretching a polyolefin-base resin film containing an inorganic fine powder and having many micro voids (fine pores) is preferred as support of any image-receiving film after transferring, based on its strength and dimensional stability (see Japanese Patent Publication No. 40794/1971, Japanese Patent Laid-Open Nos. 55433/1981, 149363/1982, and 181829/1982, and U.S. Pat. No. 3,765,999).
Good flexibility and heat resistance are obtained in the synthetic papers by forming micro voids inside the film. As a result thereof the cushion property towards a printing head is improved and it becomes possible to highly efficiently utilize the heat energy.
An image-receiving film supported by a stretched polyolefin resin film containing an inorganic fine powder, which is coated with a water-soluble primer of a nitrogen-containing high molecular compound for imparting various printing aptitudes and antistatic properties is described in Japanese Patent Laid-Open No. 149363/1982 and U.S. Pat. Nos. 4,420,536, 4,906,526, and 5,834,098. Such image-receiving-film is used for a melt heat-transfer system. However, the primer layer is hygroscopic and contains a large amount of water in a high temperature high-humidity environment. Accordingly, the following problems arise: the transfer of the heat-melting ink is disturbed and it is difficult to transfer the heat-melting ink onto an image-receiving film. As a result thereof, line cutting of prints, such as bar codes, occurs and the images become indistinct.
Japanese Patent Laid-Open No. 80684/1996 discloses that clear images can be obtained even in a high-temperature high-humidity environment This is achieved by using an image-receiving film obtained by coating a water-soluble primer of a nitrogen-containing high-molecular compound on a fine porous support. The fine-porous support is made of the stretched product of a polyolefin resin film containing from 30 to 65% by weight a colloidal calcium carbonate fine powder. The calcium carbonate fine powder has a mean particle size of from 0.02 to 0.5 xcexcm and a specific area of from 60,000 to 300,000 cm2/g.
However, the hygroscopicity of the primer layer is increased when using an image-receiving film having a support comprising a stretched polyolefin resin film and having a water-soluble primer of a nitrogen-containing high molecular compound in a high-temperature high-humidity environment for a long time. The primer layer becomes the transferring surface (printing surface) of the heat-melting ink. It is considered that the surface of the primer layer retains evaporated water.
The printed matter exhibits inferior ink adhesion when left in a high-temperature-high-humidity environment for a long time. When the printed surface is treated with a cellophane tape, the ink is easily released.
The present invention solves the above problems of the related art by providing a thermoplastic resin film having excellent printing properties.
It is an object of the present invention to provide a heat transfer film having excellent transferring properties and excellent adhesion of ink which gives clear images in a heat transfer printer.
It is another object of the present invention to provide a thermoplastic resin film which is a melt heat transfer film having excellent transferring properties and excellent adhesion of ink in various printing systems.
These and other objects have achieved by the present invention, the first embodiment of which includes an image-receiving film for printing and heat transfer, comprising:
a support comprising a thermoplastic resin film;, and
a coated layer formed on said thermoplastic resin film;
wherein said coated layer comprises a component (A);
wherein said component (A) is an aqueous resin dispersion;
wherein said aqueous resin dispersion is obtained by dispersing an olefin copolymer (a) having an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride in water;
wherein said dispersing of said olefin copolymer (a) proceeds using at least one dispersing agent ()) selected from the group consisting of a nonionic surface active agent, a nonionic water-soluble high molecular compound, a cationic surface active agent, and a cationic water-soluble high molecular compound;
wherein a weight ratio of (a)/(b) is from 100/1 to 100/30 based on a total weight of solid components in said aqueous resin dispersion; and
wherein said olefin copolymer (a) and said dispersing agent (b) each independently have a mean particle size of not more than 5 xcexcm.